1. Field of the Invention
This invention relates to a process for the synthesis of acrylamide by reacting acrylonitrile with water in the presence of a Raney copper catalyst, and more particularly relates to remarkable enhancement of catalytic activity.
2. Description of the Prior Art
Acrylamide is a useful monomer employed for a wide field of applications in addition to be used for the preparation of acrylamide base polymers utilized for a paper reinforcing agent and a coagulating agent.
Acrylamide is now synthesized by reacting acrylonitrile which is now cheaply produced in industry with water in the presence of a solid catalyst.
Various copper base catalysts have been known as the solid catalyst used for the synthesis of acrylamide by reacting acrylonitrile with water. Raney copper catalyst is a typical one of such catalysts and disclosed in U.S. Pat. No. 3,767,706, U.S. Pat. No. 3,911,009 and U.S. Pat. No. 4,056,565.
The Raney copper catalyst is generally prepared by the following method. A molten alloy composed of copper and aluminum is poured into a mold, cooled and solidified, that is, cast. The resultant mass of alloy is then crushed to particles or powder with a jaw crusher or ball mill. Thereafter aluminum component is removed by leaching with sodium hydroxide and the like.
However, according to the information of the present inventors, the Raney copper catalyst obtained by the method does not exhibit satisfactorily high activity when the catalyst is used for the synthesis of acrylamide. Therefore the reaction temperature must be raised, whereby generation of impurities is increased and causes degradation of product quality.
Japanese Patent Publication No. 33612/1977 describes an example for intending to increase the activity by the addition of Sn, Fe, Co, Ru, Rh, Ir, Os or Pt to Raney copper catalyst. The addition of these metal components causes activity improvement to some extent. The resultant activity, however, is still much lower than satisfactory level.
Many examples are also found on the incorporation of secondary components to metallic copper catalysts other than Raney copper catalyst. In Japanese Patent Publication No. 43924/1978, copper salts are reduced by hypophosphite together with salts of metals such as Cr, V, Si, Fe, Ti and Zr, and subsequently decomposed by heat to give a metallic copper catalyst containing the secondary components. In Japanese Patent Publication No. 43927/1978, a metallic copper catalyst containing the secondary components is similarly obtained by reducing copper salts with boron hydrogen compounds under alkaline conditions together with salts of elements selected from the group IIa, IIb, IIIa, IIIb, IVa, IVb, Va, Vb, VIa, VIIa, and VIII elements in the periodic table. In Japanese Patent Publication No. 41241/1977 a metallic copper catalyst containing secondary components is obtained by reducing copper oxides in a hydrogen atmosphere together with oxides of metals such as Si, W, Hg, Zr, Fe, Ni, and Zn.
According to the information obtained by the present inventors, these metallic copper catalysts other than the Raney copper catalyst have much inferior activity to that of the Raney copper catalyst when the former catalysts are composed of copper alone. Some catalysts can be considerably enhanced their activity by the addition of other components for modifying these catalysts. Nevertheless, the resultant activity of these catalysts is slightly higher than that of the Raney copper catalyst.